fpdb/pyfpdb/interlocks.py

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# -*- coding: utf-8 -*-
# Code from http://ender.snowburst.org:4747/~jjohns/interlocks.py
# Thanks JJ!
import sys
import os, os.path
import subprocess
import time
import signal
import base64
InterProcessLock = None
"""
Just use me like a thread lock. acquire() / release() / locked()
Differences compared to thread locks:
1. By default, acquire()'s wait parameter is false.
2. When acquire fails, SingleInstanceError is thrown instead of simply returning false.
3. acquire() can take a 3rd parameter retry_time, which, if wait is True, tells the locking
mechanism how long to sleep between retrying the lock. Has no effect for unix/InterProcessLockFcntl.
Differences in fpdb version to JJ's original:
1. Changed acquire() to return false like other locks
2. Made acquire fail if same process already has the lock
"""
class SingleInstanceError(RuntimeError):
"Thrown when you try to acquire an InterProcessLock and another version of the process is already running."
class InterProcessLockBase:
def __init__(self, name=None ):
self._has_lock = False
if not name:
name = sys.argv[0]
self.name = name
self.heldBy = None
def getHashedName(self):
return base64.b64encode(self.name).replace('=','')
def acquire_impl(self, wait): abstract
def acquire(self, wait=False, retry_time=1, source=None):
if source == None:
source="Unknown"
if self._has_lock: # make sure 2nd acquire in same process fails
print "lock already held by:",self.heldBy
return False
while not self._has_lock:
try:
self.acquire_impl(wait)
self._has_lock = True
self.heldBy=source
#print 'i have the lock'
except SingleInstanceError:
if not wait:
# raise # change back to normal acquire functionality, sorry JJ!
return False
time.sleep(retry_time)
return True
def release(self):
self.release_impl()
self._has_lock = False
self.heldBy=None
def locked(self):
if self.acquire():
self.release()
return False
return True
LOCK_FILE_DIRECTORY = '/tmp'
class InterProcessLockFcntl(InterProcessLockBase):
def __init__(self, name=None):
InterProcessLockBase.__init__(self, name)
self.lockfd = 0
self.lock_file_name = os.path.join(LOCK_FILE_DIRECTORY, self.getHashedName() + '.lck')
assert(os.path.isdir(LOCK_FILE_DIRECTORY))
# This is the suggested way to get a safe file name, but I like having a descriptively named lock file.
def getHashedName(self):
import re
bad_filename_character_re = re.compile(r'/\?<>\\\:;\*\|\'\"\^=\.\[\]')
return bad_filename_character_re.sub('_',self.name)
def acquire_impl(self, wait):
self.lockfd = open(self.lock_file_name, 'w')
fcntrl_options = fcntl.LOCK_EX
if not wait:
fcntrl_options |= fcntl.LOCK_NB
try:
fcntl.flock(self.lockfd, fcntrl_options)
except IOError:
self.lockfd.close()
self.lockfd = 0
raise SingleInstanceError('Could not acquire exclusive lock on '+self.lock_file_name)
def release_impl(self):
fcntl.lockf(self.lockfd, fcntl.LOCK_UN)
self.lockfd.close()
self.lockfd = 0
try:
os.unlink(self.lock_file_name)
except IOError:
# We don't care about the existence of the file too much here. It's the flock() we care about,
# And that should just go away magically.
pass
class InterProcessLockWin32(InterProcessLockBase):
def __init__(self, name=None):
InterProcessLockBase.__init__(self, name)
self.mutex = None
def acquire_impl(self,wait):
self.mutex = win32event.CreateMutex(None, 0, self.getHashedName())
if win32api.GetLastError() == winerror.ERROR_ALREADY_EXISTS:
self.mutex.Close()
self.mutex = None
raise SingleInstanceError('Could not acquire exclusive lock on ' + self.name)
def release_impl(self):
self.mutex.Close()
class InterProcessLockSocket(InterProcessLockBase):
def __init__(self, name=None):
InterProcessLockBase.__init__(self, name)
self.socket = None
self.portno = 65530 - abs(self.getHashedName().__hash__()) % 32749
def acquire_impl(self, wait):
self.socket = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
try:
self.socket.bind(('127.0.0.1', self.portno))
except socket.error:
self.socket.close()
self.socket = None
raise SingleInstanceError('Could not acquire exclusive lock on ' + self.name)
def release_impl(self):
self.socket.close()
self.socket = None
# Set InterProcessLock to the correct type given the sysem parameters available
try:
import fcntl
InterProcessLock = InterProcessLockFcntl
except ImportError:
try:
import win32event
import win32api
import winerror
InterProcessLock = InterProcessLockWin32
except ImportError:
import socket
InterProcessLock = InterProcessLockSocket
def test_construct():
"""
# Making the name of the test unique so it can be executed my multiple users on the same machine.
>>> test_name = 'InterProcessLockTest' +str(os.getpid()) + str(time.time())
>>> lock1 = InterProcessLock(name=test_name)
>>> lock1.acquire()
True
>>> lock2 = InterProcessLock(name=test_name)
>>> lock3 = InterProcessLock(name=test_name)
# Since lock1 is locked, other attempts to acquire it fail.
>>> lock2.acquire()
False
>>> lock3.acquire()
False
# Release the lock and let lock2 have it.
>>> lock1.release()
>>> lock2.acquire()
True
>>> lock3.acquire()
False
# Release it and give it back to lock1
>>> lock2.release()
>>> lock1.acquire()
True
>>> lock2.acquire()
False
# Test lock status
>>> lock2.locked()
True
>>> lock3.locked()
True
>>> lock1.locked()
True
>>> lock1.release()
>>> lock2.locked()
False
>>> lock3.locked()
False
>>> lock1.locked()
False
>>> if os.name == 'posix':
... def os_independent_kill(pid):
... import signal
... os.kill(pid, signal.SIGKILL)
... else:
... assert(os.name == 'nt')
... def os_independent_kill(pid):
... ''' http://www.python.org/doc/faq/windows/#how-do-i-emulate-os-kill-in-windows '''
... import win32api
... import win32con
... import pywintypes
... handle = win32api.OpenProcess(win32con.PROCESS_TERMINATE , pywintypes.FALSE, pid)
... #return (0 != win32api.TerminateProcess(handle, 0))
# Test to acquire the lock in another process.
>>> def execute(cmd):
... cmd = 'import time;' + cmd + 'time.sleep(10);'
... process = subprocess.Popen([sys.executable, '-c', cmd])
... pid = process.pid
... time.sleep(2) # quick hack, but we test synchronization in the end
... return pid
>>> pid = execute('import interlocks;a=interlocks.InterProcessLock(name=\\''+test_name+ '\\');a.acquire();')
>>> lock1.acquire()
False
>>> os_independent_kill(pid)
>>> time.sleep(1)
>>> lock1.acquire()
True
>>> lock1.release()
# Testing wait
>>> pid = execute('import interlocks;a=interlocks.InterProcessLock(name=\\''+test_name+ '\\');a.acquire();')
>>> lock1.acquire()
False
>>> os_independent_kill(pid)
>>> lock1.acquire(True)
True
>>> lock1.release()
"""
pass
if __name__=='__main__':
import doctest
doctest.testmod(optionflags=doctest.IGNORE_EXCEPTION_DETAIL)